It is proposed to use the white rat as an experimental model for studies of the metabolism of the minor brain sterol cholest-5-ene-3 Beta,24-diol (cerebrosterol) in brain tissue. Cholest-5-ene-3 Beta,24- diol is present in rat brain and its biosynthesis has been recently demonstrated by us in rat brain. Preparation of tritium and/or carbon- 14 labeled cholest-5-ene-3 Beta, 24-diol is in progress, and we have preliminary evidence that the sterol is metabolized in rat brain in vivo. We plan to demonstrate the metabolism in brain homogenates, etc., and to determine the nature of the metabolic reactions, including the sterol metabolite structures, etc. These approaches will then establish that the brain sterol is in a dynamic state in rat brain. We also seek to examine the changes in cholest-5-ene-3 Beta,24-diol biosynthesis and metabolism in developing rat brain, we have some evidence that differences in sterol metabolism may obtain on maturation.